U.S. Pat. No. 6,909,554 discloses an optical system that includes an array of opto-electronic devices in the form of an array of light emitters like LEDs or an array of light detectors like CCDs, wherein the array is substantially extending along a planar plane. Further, the optical system includes an array of micro lenses and a fore optic having a non planar focal field. Each opto-electronic device is provided with one of the micro-lenses which each have a focal length and/or a separation distance between them and their respective opto-electronic device such that it compensates for the non planar focal field of the fore optic, so that light which is provided by the fore optic is reconfigured by the micro-lenses to be substantially focused along the planar plane of the array of opto-electronic devices, and vice versa.
One disadvantage of this optical system is that in case of using LEDs as light emitting opto-electronic devices, a great part of the emitted light cannot be captured by the related micro-lens but is lost. This is due to the fact, that an LED is usually a Lambertian light source having a pattern of the radiation intensity which is more or less proportional to the cosine of the angle between the observer and the centerline or surface normal in which the LED lies.
US 2007/0211473 discloses a light source especially for traffic lights and other signal heads, comprising a housing in which an LED module is positioned for emitting light through a Fresnel lens and a spreading lens to the outside of the housing, wherein an improved uniformity of the light distribution across the surface of the spreading lens shall be achieved by positioning around each LED a reflector cup having either a tilt angle such that more light is directed toward the outer perimeter of the spreading lens, or having a non symmetrical curvature or being fanned out in order to achieve the effect of the tilted reflector cup without tilting the same.